1. Field of Invention
The present invention relates to a passenger detector and, more particularly, to an image detector for identifying the type of a passenger on a seat of a car.
2. Related Prior Art
Air bags have been proven to effectively protect passengers in car accidents. An air bag is inflated fast via ignition and explosion of explosive when a car is hit severely. The inflation is fast so that the air bag during the inflation might however harm an infant, a child or even an adult. Traditionally, the explosion of the explosive is constant regardless the state of a passenger so that the air bag might cause an injury to a passenger but provide insufficient protection to another passenger. Hence, there have been various attempts to provide detectors for detecting the state of a passenger so that the explosion can be executed to a degree according to the detected state of the passenger.
Conventional detectors are generally weight detectors used to measure the weight of the passenger so that the explosion of the explosive is executed according to the measured weight of the passenger. The measurement of the weight of the passenger by the weight detectors could be affected by the pose of the passenger or vibration during the travel of the car. On the other hand, the weight detectors are expensive and it is difficult to locate them in the cars.
There have been attempts to use image detectors to use computerized images of the passengers to determine the state of the passengers. Some of the image detectors are based on monocular vision while the others are based on stereo vision. Based on the monocular vision, a single camera is used to provide an edge image, a silhouette, or a differential image of a passenger that is not affected by light and shadow. Based on the stereo vision, two cameras are used, as imitation of human eyes, to take two images of the passenger to produce a disparity map.
An image detector, based on the monocular vision or the stereo vision, analyzes characters of a computerized image of a passenger to determine the state of the passenger. The analysis is conducted according to an algorithm such as nearest neighbor, k nearest neighbor, non-linear discriminate analysis and support vector machine. To overcome problems related to the angle and intensity of light and the look of the passenger, the image detectors are operated with an assumption that the camera(s) and a seat on which the passenger sits are not moved relative to each other. This assumption is however not practical since the camera(s) and the seat are moved relative to each other because of vibration during the travel of the car.
The present invention is therefore intended to obviate or at least alleviate the problems encountered in prior art.